A. Field of the Invention
The present invention relates to a method and apparatus for interfacing an external Host Signal Processor modem (hereinafter referred to as HSP modem), a joystick, and a MIDI interface, especially to a method and apparatus adaptable to a standard game port of a personal computer for allowing system to simultaneously communicate with an external HSP modem, a joystick and a MIDI interface.
B. Description of the Prior Art
Commercially available modem adapters are characterized as either internal or external modems. The external modem is a standalone device which communicates with a host computer via a serial communication port. It includes two phone jacks residing on the circuit board of the modem for connecting to a telephone line and a telephone set. The circuit board of the external modem contains a dedicated processor, usually a digital signal processor (hereinafter referred to as DSP), for performing mathematical manipulations of data to be in a format compatible with analog public switched telephone networks (hereinafter referred to as PSTNs ).
Since the DSP is a relatively expansive chip, an internal modem, also called an HSP modem, is developed to replace an external modem. The HSP modem includes two major portions: a modem module which is mounted on an internal modem adapting card for plugging into a card slot and communicating with a system bus, and a software portion which is executed by CPU to compute the data, commands, and protocols from the modem module. In contrast to the external modem, the data from modem module is raw data with high frequencies which is so large in size that these data must be accessed by CPU via ISA bus or PCI bus rather than serial communication ports.
To furnish the function of an HSP modem, many motherboard manufactures provide an on-board internal modem adapting card and an HSP modem interface. At the time when a user purchases a personal computer, he/she can communicate with the Internet simply by plugging the phone jack of a telephone line to the connector of the internal card. The operating system running on the personal computer can even allow the plug-and-play function of the internal modem adapting card. However, this advantage may sometimes become a waste when a user would connect to the Internet via dedicated networks instead of PSTNs. In such case, it would also be a waste for motherboard manufactures to provide a device which is not in use.
An HSP modem depends on the software engine to perform the functions of modulation and demodulation and the software engine cannot communicate with an external modem. For this reason, if the motherboard manufactures would not provide the internal modem adapting card and interface, the user would have to rely on an external modem to connect to PSTNs. Moreover, major manufacturers of HSP modems, such as PCTEL, Motorola, and Rockwell, do not provide connection links and protocols to communicate a standard PC port for external modems. In other words, there is no interface port on the game port available for communicating the software engine of an HSP modem with an external modem if a user would upgrade his/her computer system to support modem functions later on.
It would be advantageous to provide a new protocol for communicating the software engine of an HSP modem with a standard interface port without having to revise the software engine of an HSP modem and allow an external modem to be readily adaptable to an HSP modem software engine. Consequently, motherboard manufactures would not have to provide on-board internal modem adapting card in advance, thereby to reduce manufacture cost. A user can also upgrade his/her system easily by plugging an external modem adapter into a standard interface port to operate with HSP modem software engine.
Accordingly, it is an object of the present invention to provide a method and apparatus which can interface an external HSP modem, a joystick and a MIDI interface, thereby allowing system to simultaneously communicate with an HSP modem, a joystick and a MIDI interface.
It is another object of the present invention to provide a new protocol of game port for communicating an external HSP modem with a standard HSP modem software engine.
It is a further object of the present invention to provide an external HSP modem which can communicate with an HSP modem software engine and completely transparent to peripheral devices on game port, thereby saving a PC card slot.
It is yet still another object of the present invention to provide a solution for motherboard manufactures so that they would not have to implement an internal modem adapter card before requested by users.
The preferred embodiment of the present invention includes: an external HSP modem housed in a compact case for coupling to a game port, and an encode/decode device on a sound chip. The case includes one connector residing on one end for mounting on a standard game port, another connector residing on the opposite end for coupling to a joystick and a MIDI interface, and a RJ-11 connector for connecting to a telephone set and PSTNs.
Inside the case, it mainly comprises a modem module, and a bridge interface. The modem module connects to the RJ-11 connector for communicating with the PSTNs and generating a plurality of modulated/demodulated signals which includes data signals and command signals. The modulated/demodulated signals are input to the bridge interface for transferring to/from the game port. The bridge interface encodes/decodes the modulated/demodulated signals input in response to the serial port clocks and then sends the encoded/decoded modulated/demodulated signals to/from an encode/decode device on a sound chip. The encode/decode device then restores the modulated/demodulated signals to its original format and transfers them to a system bus for CPU to access via an HSP modem interface.
Accordingly, the present invention provides a method for interfacing a modem module, a joystick and a MIDI interface on a standard game port of a personal computer. The method comprises the steps of: (1) Redefining a plurality of read-only ports on said game port for transmitting a plurality of modulated/demodulated signals of a modem module. (2) Sending the modulated/demodulated signals to an encode/decode device in the personal computer via the read-only ports for outputting decoded modulated/demodulated signals. (3) Transferring the decoded modulated/demodulated signals to a system bus via an HSP modem interface.